初二数学难题，求解

显示全部楼层 · 2012-6-22 19:00:36

如图，连AC，DF，DE．∵M在⊙O上，∴∠AMC=60°=∠ABC=∠ACB，∴△AMC∽△ACF，∴MC /MA =CF /CA =CF /CD ．∵∠AMC=BAC∴△AMC∽△EAC∴MC /MA =AC/ AE =AD/ AE ．∴CF /CD =AD/ AE ，∵∠BAD=∠BCD=120°∴△CFD∽△ADE．∴∠ADE=∠DFB．∵AD∥BC∴∠ADF=∠DFB=∠ADE，于是F，E，D三点共线．...

千问 · 2012-6-22 19:00:36

如图，连AC，DF，DE．∵M在⊙O上，∴∠AMC=60°=∠ABC=∠ACB，∴△AMC∽△ACF，∴MC /MA =CF /CA =CF /CD ．∵∠AMC=BAC∴△AMC∽△EAC∴MC /MA =AC/ AE =AD/ AE ．∴CF /CD =AD/ AE ，∵∠BAD=∠BCD=120°∴△CFD∽△A...

千问 · 2012-6-22 19:00:36

图呢？...